A reappraisal of Paspalum pilosum and P-peregrinum (Poaceae: Panicoideae: Paniceae)

Paspalum pilosum and P. peregrinum are members of the informal Decumbentes group of Paspalum, and grow from Mexico and Mesoamerica to Brazil and Bolivia in South America. Paspalum pilosum is characterized by its erect to decumbent culms, glabrous to pilose sheaths and blades, one or two racemes in terminal inflorescences, glabrous spikelets arranged in pairs in 2 irregular series on the rachis, dimorphic lower glumes in the pair of spikelets, longitudinally sulcate lower lemmas, and glabrous gynoecium. Paspalum peregrinum has sheaths and blades densely pilose. racemes occasionally branched, hairy spikelets arranged in 1 to 4 series on the rachis, and a hairy gynoecium. These modifications in the morphology of P. peregrinum are due to a fungal infection. Another species, Thrasya venezuelana, known only from the type collection. is the same taxon as P. peregrinum. We conclude that P. peregrinum and T. venezuelana are in fact abnormal specimens of P. pilosum, whose morphology is modified by the fungal infection. Therefore, both species are reduced to the synonymy of P. pilosum. This constitutes two new incidents of erroneous interpretation of abnormal morphology caused by fungi, and the first in the tribe Paniceae.